CN111351553A - A high-order modal micromass sensor based on modal localization effect - Google Patents

Abstract

The invention discloses a high-order modal micro-mass sensor based on modal localization effect, which belongs to the field of micro-electro-mechanical systems and comprises a first clamped beam, a second clamped beam, an upper coupling electrode I, an upper coupling electrode II, a lower coupling electrode I, a lower coupling electrode II, a fixed electrode I, a fixed electrode II, a coupling voltage source and a driving voltage source; two ends of the first fixed supporting beam are fixed through a fixed end I and a fixed end II respectively; two ends of the second fixed supporting beam are fixed through a fixed end III and a fixed end IV respectively; the upper coupling electrode I and the upper coupling electrode II are fixed at two ends of the lower surface of the first clamped beam; the lower coupling electrode I and the lower coupling electrode II are fixed at two ends of the upper surface of the second clamped beam; a coupling voltage source is applied between the lower surface of the first clamped beam and the upper surface of the second clamped beam to realize corresponding electrostatic coupling connection; the fixed electrode I and the fixed electrode II are respectively connected with a driving voltage source; the fixed electrode I and the fixed electrode II are fixed below the second clamped beam, the structure of the invention is simple, the driving mode is easy to adjust, any structure optimization is not needed, and the invention has the advantages of simple process, stable configuration, easy processing and the like, thereby being widely applied to various aspects.

Description

A high-order modal micromass sensor based on modal localization effect

technical field

The present invention relates to the field of micro-electromechanical systems, in particular to a high-order modal micro-mass sensor based on modal localization effect.

Background technique

Due to its small size, low power consumption, and high efficiency and reliability, MEMS resonant sensors have been widely used in micro-mass sensors, including identification and detection of biomolecules (DNA, cells, bacteria and viruses, etc.), detection of tiny particles and Liquid, gas composition and concentration detection, etc.

Although reducing the size of the sensor can increase the sensitivity, the size cannot be infinitely reduced due to the limitation of the manufacturing process. How to improve the sensitivity of the micro-mass sensor without changing the structure size has attracted the attention of many scholars. Lochon et al. in "An alternative solution to improve sensitivity of resonant microcantilever chemical sensors: comparison between using high-ordermodes and reducing dimensions" (Sensors and Actuators B: Chemical, Volume 108, Issues 1–2, 22 July 2005, Pages 979-985) Two methods of reducing size and adopting higher-order modes are compared in this paper, and the results show that both methods can improve the sensitivity.

In recent years, a new sensitivity detection method based on the modal localization phenomenon can greatly improve the sensitivity. Different from the traditional frequency shift method as the sensitivity output, the sensor based on the modal localization phenomenon uses the amplitude ratio as the sensitivity output. . M. Spletzer et al in "Ultrasensitive mass sensing using modelocalization in coupled microcantilevers," (Applied Physics Letters, vol. 88, no. 25, p. 254102, 2006) proposed a mechanically coupled cantilever structure and adopted mode localization Different from the single resonance sensor that uses the frequency change as the sensitivity output, this sensor uses the eigenvalue change as the sensitivity output, which improves the sensitivity by two orders of magnitude compared with the frequency change output method. Zhao Chun et al. in "A mass sensorbased on3-DOF mode localized coupled resonator under atmospheric pressure" (Sensors and Actuators A:Physical,2018,279:254-262.) by increasing the degree of freedom of the coupled oscillator, using three mechanical The coupled resonator detects the mass, and the results show a three orders of magnitude improvement in sensitivity compared to a single-DOF resonator. The modal localization phenomenon can be found in approximately symmetric weakly coupled systems, when the sensor is subjected to small mass perturbations, the symmetry of the system will be broken and the eigenstates and amplitude ratios will change sharply. It has gradually attracted more and more attention due to its wide range of applications, which can detect extremely tiny masses such as DNA, cancer and biomolecules.

Through literature research, it is found that the previous research on modal localization only involves the study of the motion of the system in the low-order mode. Whether it is applied to the micro-mass sensor or the acceleration sensor, it works by exciting its vibration in the low-order mode. . We know that for MEMS devices, it is generally more sensitive to excite the motion in high-order modes than in low-order modes, but because it is very challenging to excite high-order modes, it requires a high excitation voltage, which is extremely This greatly limits the application of MEMS devices in higher-order modes. Therefore, the same difficulty is also faced for weakly coupled structures utilizing modal localization effects. How to apply the modal localization effect to higher-order modes to further improve the sensitivity of MEMS devices is a very meaningful study.

SUMMARY OF THE INVENTION

According to the problems existing in the prior art, the present invention discloses a high-order modal micro-mass sensor based on modal localization effect, including:

The first clamped beam, the second clamped beam, the upper coupling electrode I, the upper coupling electrode II, the lower coupling electrode I, the lower coupling electrode II, the fixed electrode I, the fixed electrode II, the coupling voltage source and the driving voltage source;

The two ends of the first fixing beam are respectively fixed by the fixed end I and the fixed end II;

The two ends of the second fixed support beam are respectively fixed by the fixed end III and the fixed end IV;

The upper coupling electrode I and the upper coupling electrode II are fixed on both ends of the lower surface of the first retaining beam;

The lower coupling electrode I and the lower coupling electrode II are fixed on both ends of the upper surface of the second retaining beam;

The coupling voltage source is applied between the lower surface of the first retaining beam and the upper surface of the second retaining beam to realize a corresponding electrostatic coupling connection;

The fixed electrode I and the fixed electrode II are respectively connected with the driving voltage source;

The fixed electrode I and the fixed electrode II are fixed below the second retaining beam.

Further, the length of the first fixing beam and the length of the second fixing beam are equal.

Further, the width of the first fixing beam and the width of the second fixing beam are equal.

Further, the length of the upper coupling electrode I, the length of the upper coupling electrode II, the length of the lower coupling electrode I and the length of the lower coupling electrode II are equal; the length of the upper coupling electrode I is equal to the length of the upper coupling electrode I. One third of the length of the second retaining beam.

Further, the width of the upper coupling electrode I, the width of the upper coupling electrode II, the width of the lower coupling electrode I and the width of the lower coupling electrode II are equal.

Further, the length of the fixed electrode I and the length of the fixed electrode II are both equal to one third of the length of the second retaining beam; the width of the fixed electrode I and the width of the fixed electrode II are both equal to the width of the second retaining beam.

Further, the distance between the fixed electrode I, the fixed electrode II and the second fixed support beam is less than or equal to the distance between the second fixed support beam and the first fixed support beam.

Further, the fixed electrode I and the fixed electrode II are jointly driven by alternating current and direct current generated by the driving voltage source.

Due to the adoption of the above technical solution, a high-order modal micro-mass sensor based on modal localization effect provided by the present invention can be widely used in chemical and biological fields to detect tiny substances, such as viruses, biomolecules, protein tissues, The quality measurement of DNA and other substances; it is composed of two equal-length two-fixed beams and coupled by static electricity, and has the characteristics of easy adjustment of the coupling strength, and the coupling strength between the fixed-support beams can be changed only by voltage adjustment; the invention The structure uses local electrostatic drive to excite the coupled structure to vibrate greatly in high-order modes; and from a theoretical point of view, the feasibility of vibration in high-order modes is verified. The first-order sensitivity is increased by 15 times, and the sensitivity is increased by more than 4000 times compared with the traditional frequency-shift output. The invention has a simple structure, easy to adjust the driving mode, no need for any structural optimization, and has the advantages of simple process, stable configuration and easy processing. , which can be widely used in various aspects.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a schematic diagram of a high-order modal micro-mass sensor model based on modal localization effect of the present invention;

Figure 2 is a globally driven sensor based on modal localization effect;

Fig. 3 is the characteristic value change of the present invention under the action of only bias voltage;

4 is a comparison diagram of the amplitude-frequency characteristics of the first clamped beam of the present invention and the third clamped beam of the sensor shown in FIG. 2 under the same driving force and coupled electrostatic force;

FIG. 5 is a comparison diagram of the amplitude-frequency characteristics of the second clamped beam of the present invention and the fourth clamped beam of the sensor described in FIG. 2 under the same driving force and coupled electrostatic force;

Figure 6(a) is an amplitude-frequency characteristic diagram of the present invention in a balanced state under low-order modal vibration when the coupling voltage is 10V;

Figure 6(b) is a phase-frequency characteristic diagram of the present invention in a balanced state under low-order modal vibration when the coupling voltage is 10V;

Figure 7(a) is an amplitude-frequency characteristic diagram of the present invention in a balanced state under high-order modal vibration when the coupling voltage is 10V;

Figure 7(b) is a phase-frequency characteristic diagram of the present invention in a balanced state under high-order modal vibration when the coupling voltage is 10V;

Figure 8(a) is a comparison diagram of the amplitude ratios of different modes under in-phase changes when the coupling voltage is 10V;

Figure 8(b) is a comparison diagram of the amplitude ratios of different modes under out-of-phase changes when the coupling voltage is 10V in the present invention;

Figure 8(c) is a comparison diagram of the frequency of different modes under in-phase changes when the coupling voltage is 10V;

FIG. 8(d) is a comparison diagram of the frequencies of different modes under out-of-phase changes when the coupling voltage is 10V according to the present invention.

In the figure: 1-1, fixed end I, 1-2, fixed end II, 1-3, fixed end III, 1-4, fixed end IV, 2, the first fixed support beam, 3, the second fixed support beam , 4-1, lower coupling electrode I, 4-2, lower coupling electrode II, 5-1, upper coupling electrode I, 5-2, upper coupling electrode II, 6-1, fixed electrode I, 6-2, fixed Electrode II, 7. Driving voltage source, 8. Coupling voltage source, 9. Third clamped beam, 10. Fourth clamped beam.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some but not all of the embodiments of the present invention. The embodiments of the present invention, and all other embodiments obtained by those of ordinary skill in the art without creative efforts, fall within the protection scope of the present invention.

1 is a schematic diagram of a high-order modal micro-mass sensor model based on modal localization effect of the present invention, a high-order modal micro-mass sensor based on modal localization effect, comprising a first clamped beam 2, a second clamped beam 3, Upper coupling electrode I5-1, upper coupling electrode II5-2, lower coupling electrode I4-1, lower coupling electrode II4-2, fixed electrode I6-1, fixed electrode II6-2, driving voltage source 7 and coupling voltage source 8;

The two ends of the first fixing beam 2 are respectively fixed by the fixed end I1-1 and the fixed end II1-2;

The two ends of the second fixing beam 3 are respectively fixed by the fixed end III1-3 and the fixed end IV1-4;

The upper coupling electrode I5-1 and the upper coupling electrode II5-2 are fixed on both ends of the lower surface of the first retaining beam 2;

The lower coupling electrode I4-1 and the lower coupling electrode II4-2 are fixed on both ends of the upper surface of the second clamping beam 3;

The coupling voltage source 8 is applied between the lower surface of the first retaining beam 2 and the upper surface of the second retaining beam 3 to realize a corresponding electrostatic coupling connection;

The fixed electrode I6-1 and the fixed electrode II6-2 are respectively connected to the driving voltage source 7;

The fixed electrode I 6 - 1 and the fixed electrode II 6 - 2 are respectively fixed under the second fixed support beam 3 .

Further, the length of the first fixing beam 2 and the length of the second fixing beam 3 are equal.

Further, the width of the first fixing beam 2 is equal to the width of the second fixing beam 3 .

Further, the length of the upper coupling electrode I5-1, the length of the upper coupling electrode II5-2, the length of the lower coupling electrode I4-1 and the length of the lower coupling electrode II4-2 are the same; the The length of the upper coupling electrode I5-1 is equal to one third of the length 2 of the second retaining beam.

Further, the width of the upper coupling electrode I5-1, the width of the upper coupling electrode II5-2, the width of the lower coupling electrode I4-1 and the width of the lower coupling electrode II4-2 are equal.

Further, the length of the fixed electrode I6-1 and the length of the fixed electrode II6-2 are equal to one third of the length of the second retaining beam 3; the width of the fixed electrode I6-1 and the fixed The width of the fixed electrode II 6 - 2 is equal to the width of the second retaining beam 3 .

Further: the distance between the fixed electrode I6-1, the fixed electrode II6-2 and the second fixing beam 3 is less than or equal to the distance between the second fixing beam 3 and the first fixing beam 2 the distance between.

Further: the fixed electrode I6-1 and the fixed electrode II6-2 are jointly driven by the alternating current and direct current generated by the driving voltage source I7.

Fig. 2 is a globally driven sensor based on modal localization effect. In Fig. 2, the third clamped beam 9 is the fourth clamped beam 10. The electrostatic coupling area between the two clamped beams is the surface area of the entire beam and the entire The fourth clamped beam 10 is driven by the fixed electrode. Compared with the sensor shown in FIG. 2, the local driving and local electrostatic coupling adopted in the present invention can achieve a higher excitation amplitude under the same driving force. Therefore, it has a higher resolution. Figure 3 shows the change of the eigenvalue under the action of only the bias voltage of the present invention. According to the dimensions in the structural parameter table 1 of the present invention, the change of the eigenvalue under the action of only the DC bias voltage, The abscissa is the bias voltage (V), and the ordinate is the frequency (KHz). Among them, ω _i,j represents the natural frequency, i represents the i-th clamped beam, and j represents the j-th order natural frequency.

Table 1 Structural parameters of micro-mass sensor

The micro-mass sensor structure based on high-order modal vibration of the present invention is a symmetric structure, therefore, the anti-symmetric mode (eg, the second-order mode) cannot be excited, and the proposed structure can excite it to vibrate near the third-order mode. When under the same excitation force, comparing the results of the local drive structure proposed in the present invention and the sensor based on the modal localization effect, FIG. 4 shows the first clamped beam 2 of the present invention and the third sensor shown in FIG. 2 . Comparison of the amplitude-frequency characteristics of the clamped beam 9 under the same driving force and coupled electrostatic force;

FIG. 5 is a comparison diagram of the amplitude-frequency characteristics of the second clamped beam 3 of the present invention and the fourth clamped beam 10 of the sensor described in FIG. 2 under the same driving force and coupled electrostatic force;

On the first clamped beam 2 and the second clamped beam 3, the local drive structure has a larger amplitude, which can improve the resolution of the sensor;

By applying a coupling voltage V _c =10V between the lower coupling electrode I4-1, the lower coupling electrode II4-2, the upper coupling electrode I5-1 and the upper coupling electrode II5-2, when there is no mass disturbance, first select the driving voltage source in the The magnitude of the alternating current is V _ac =0.02V, and then the direct current V _dc in the driving voltage source I7 is continuously adjusted to keep the system in a balanced state, where V _dc =1V, and the amplitudes of the two fixed beams are the same.

Figure 6(a) is the amplitude-frequency characteristic diagram of the present invention in a balanced state under low-order modal vibration when the coupling voltage is 10V; Figure 7(a) is the present invention in a high-order modal vibration when the coupling voltage is 10V Figure 6(a) and Figure 7(a) are the amplitude-frequency characteristic diagrams of the excitation system under low-order modal and high-order modal vibrations, respectively.

Figure 6(b) is a phase-frequency characteristic diagram of the present invention in a balanced state under low-order modal vibration when the coupling voltage is 10V, and Figure 7(b) is a high-order modal vibration of the present invention when the coupling voltage is 10V Figure 6(b) and Figure 7(b) show the phase-frequency characteristics of the sensor in the low-order mode and the high-order mode. The amplitude-frequency characteristics of the sensor include in-phase and out-of-phase modes, respectively. In the present invention, the sensitivity conditions under in-phase and out-of-phase vibrations are respectively studied,

Figure 8(a) is a comparison diagram of the amplitude ratios of different modes under in-phase changes when the coupling voltage is 10V in the present invention; Figure 8(b) is the amplitude ratio of different modes when the coupling voltage is 10V in the present invention. The comparison diagram of the value ratio under the out-of-phase change; Fig. 8(c) is the comparison diagram of the frequency of different modes under the in-phase change when the coupling voltage is 10V of the present invention; Fig. 8(d) is the coupling voltage of the present invention. When it is 10V, the comparison diagram of the frequencies of different modes under out-of-phase changes shows that whether it is a low-order mode or a high-order mode, when the relative amplitude ratio is used as the sensitivity output, the sensitivity is higher under out-of-phase vibration.

Since frequency is a unit (Hz) dimension, and amplitude ratio is a unitless dimension, when comparing frequency sensitivity and amplitude ratio sensitivity, we define relative sensitivity, relative frequency change and relative amplitude ratio change. The sensitivity can be expressed as:

Here S _ω and S _a represent the sensitivity of the shift based on the resonant frequency and the amplitude ratio, respectively, ω ⁰ _i,j is the frequency of the clamped beam i in the equilibrium state under the j-order mode, and ω _i,j is the j-order mode The frequency of the lower clamped beam i after adding mass, w _2,j ,w _3,j is the amplitude change of the first clamped beam 2 and the second clamped beam 3 after the j-order mode is added with mass, w _{2, j} ⁰ , w _{3 , j} ⁰ are the amplitudes of the first clamped beam 2 and the second clamped beam 3 in the j-order modal equilibrium state, respectively.

In view of Fig. 8(a), Fig. 8(b), Fig. 8(c) and Fig. 8(d), the relative change of frequency and amplitude ratio at different natural frequencies with different disturbance masses added in the middle of the first clamped beam 2 Compared with the traditional relative change in frequency as the sensitivity output (because the sensitivities are basically the same under the frequency output of the first clamped beam 2 and the second clamped beam 3, the output of the relative frequency change in Figure 8 The result is that the first clamped beam 2 is used as the object), and the amplitude ratio as the sensitivity output method can greatly improve the sensitivity of the mass sensor. Under the same mass disturbance, the sensitivity can be increased by more than 3 orders of magnitude. By exciting the sensor in high-order modal vibration, ultra-high sensitivity can be obtained. Comparing the sensitivity of the third-order modal vibration under the change of the amplitude ratio of the second clamped beam 3 and the sensitivity of the first-order modal vibration, it can be seen that the sensitivity is increased by 15.23 times. . Table 2 shows the online adjustment of the sensor sensitivity by adjusting the voltage between the coupling electrodes in the embodiment of the present invention. When the coupling voltage is equal to 15V, the output amplitude ratio is 39.07. When the coupling voltage is adjusted to 9V, the output amplitude ratio can reach 225.94. It can be found that the sensitivity can be greatly improved simply by changing the coupling strength.

Table 2 Relative changes of amplitude ratios under different coupling strengths in high-order modes

Coupling voltage output amplitude ratio 9V 225.94 12V 78.51 15V 39.07

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (8)

1. a high-order modal micro-mass sensor based on modal localization effect, is characterized in that: comprising, The first clamped beam, the second clamped beam, the upper coupling electrode I, the upper coupling electrode II, the lower coupling electrode I, the lower coupling electrode II, the fixed electrode I, the fixed electrode II, the coupling voltage source and the driving voltage source; The two ends of the first fixing beam are respectively fixed by the fixed end I and the fixed end II; The two ends of the second fixed support beam are respectively fixed by the fixed end III and the fixed end IV; The upper coupling electrode I and the upper coupling electrode II are fixed on both ends of the lower surface of the first retaining beam; The lower coupling electrode I and the lower coupling electrode II are fixed on both ends of the upper surface of the second retaining beam; The coupling voltage source is applied between the lower surface of the first retaining beam and the upper surface of the second retaining beam to realize a corresponding electrostatic coupling connection; The fixed electrode I and the fixed electrode II are respectively connected with the driving voltage source; The fixed electrode I and the fixed electrode II are fixed below the second retaining beam. 2 . The high-order modal micro-mass sensor based on modal localization effect according to claim 1 , wherein the length of the first clamped beam is equal to the length of the second clamped beam. 3 . 3. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, wherein the width of the first clamped beam and the width of the second clamped beam are equal. 4. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, characterized in that: the length of the upper coupling electrode I, the length of the upper coupling electrode II, the length of the lower coupling electrode The length of the electrode I is equal to the length of the lower coupling electrode II; the length of the upper coupling electrode I is equal to one third of the length of the second retaining beam. 5. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, characterized in that: the width of the upper coupling electrode I, the width of the upper coupling electrode II, the width of the lower coupling electrode The width of the electrode I is equal to the width of the lower coupling electrode II. 6. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, wherein the length of the fixed electrode I and the length of the fixed electrode II are both equal to the second clamp One third of the length of the beam; the width of the fixed electrode I and the width of the fixed electrode II are both equal to the width of the second fixed beam. 7. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, characterized in that: between the fixed electrode I, the fixed electrode II and the second clamped beam The distance is less than or equal to the distance between the second fixed beam and the first fixed beam. 8. A high-order modal micro-mass sensor based on modal localization effect according to claim 1, characterized in that: the fixed electrode I and the fixed electrode II are generated by the alternating current and the driving voltage source. Direct current co-drive.

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